In my previously identified co-pending patent application Ser. No. 507,763 filed Apr. 12, 1990, a manual machine is disclosed for accomplishing the objectives set forth herein. However, the present invention is directed to an improvement of that disclosed machine in that the present invention includes means for automatically achieving the desired wire winding rate and synchronous operation of the two pulleys employed in the present machine. This avoids the necessity of time-consuming skilled labor in the assembly of a harness. Further, it avoids human error in the direction of winding contrahelic layers. A further advantage of the automated version of the present invention is the achievement of tightly wound layers so that the amount of copper used is minimized.
In the preparation of complex harnesses, numerous wires are required to be twisted and straight layed. Electrical wires which are bundled and in generally parallel configurations are capable of withstanding torsional displacements along a harness axis. However, this basic type of harness suffers a high failure rate when the harness undergoes sharp bends. This is due to the fact that the inside of the bend places the wires thereat in compression while the wires at the outside of the bend are placed in tension.
Contrahelic harnesses have superior performance characteristics when a harness is to be bent. A contrahelic configuration includes helically wound wires wound in a first sense and comprising a first layer while a second coaxial outer layer comprises helically wound wires which are wound in an opposite sense. Although such contrahelic configurations are superior in the area of bends, they are inferior to straight lay wires along straight sections where torsional displacement is experienced by a harness.
In many situations a length of cable is required which must include bends and straight line sections. Conventionally, this is accommodated by employing connectors between straight lay up and contrahelic lay up sections of a harness. The presence of electrical connectors encourages mechanical failures as the cable undergoes motion in torsional and bending modes.